Acceptability, feasibility, drug safety, and effectiveness of a pilot mass drug administration with a single round of sulfadoxine-pyrimethamine plus primaquine and indoor residual spraying in communities with malaria transmission in Haiti, 2018

For a malaria elimination strategy, Haiti's National Malaria Control Program piloted a mass drug administration (MDA) with indoor residual spraying (IRS) in 12 high-transmission areas across five communes after implementing community case management and strengthened surveillance. The MDA distributed sulfadoxine-pyrimethamine and single low-dose primaquine to eligible residents during house visits. The IRS campaign applied pirimiphos-methyl insecticide on walls of eligible houses. Pre- and post-campaign cross-sectional surveys were conducted to assess acceptability, feasibility, drug safety, and effectiveness of the combined interventions. Stated acceptability for MDA before the campaign was 99.2%; MDA coverage estimated at 10 weeks post-campaign was 89.6%. Similarly, stated acceptability of IRS at baseline was 99.9%; however, household IRS coverage was 48.9% because of the high number of ineligible houses. Effectiveness measured by Plasmodium falciparum prevalence at baseline and 10 weeks post-campaign were similar: 1.31% versus 1.43%, respectively. Prevalence of serological markers were similar at 10 weeks post-campaign compared with baseline, and increased at 6 months. No severe adverse events associated with the MDA were identified in the pilot; there were severe adverse events in a separate, subsequent campaign. Both MDA and IRS are acceptable and feasible interventions in Haiti. Although a significant impact of a single round of MDA/IRS on malaria transmission was not found using a standard pre- and post-intervention comparison, it is possible there was blunting of the peak transmission. Seasonal malaria transmission patterns, suboptimal IRS coverage, and low baseline parasitemia may have limited the effectiveness or the ability to measure effectiveness

Acceptability, Feasibility, Drug Safety, and Effectiveness of a Pilot Mass Drug Administration with a Single Round of Sulfadoxine-Pyrimethamine Plus Primaquine and Indoor Residual Spraying in Communities with Malaria Transmission in Haiti, 2018.

For a malaria elimination strategy, Haiti's National Malaria Control Program piloted a mass drug administration (MDA) with indoor residual spraying (IRS) in 12 high-transmission areas across five communes after implementing community case management and strengthened surveillance. The MDA distributed sulfadoxine-pyrimethamine and single low-dose primaquine to eligible residents during house visits. The IRS campaign applied pirimiphos-methyl insecticide on walls of eligible houses. Pre- and post-campaign cross-sectional surveys were conducted to assess acceptability, feasibility, drug safety, and effectiveness of the combined interventions. Stated acceptability for MDA before the campaign was 99.2%; MDA coverage estimated at 10 weeks post-campaign was 89.6%. Similarly, stated acceptability of IRS at baseline was 99.9%; however, household IRS coverage was 48.9% because of the high number of ineligible houses. Effectiveness measured by Plasmodium falciparum prevalence at baseline and 10 weeks post-campaign were similar: 1.31% versus 1.43%, respectively. Prevalence of serological markers were similar at 10 weeks post-campaign compared with baseline, and increased at 6 months. No severe adverse events associated with the MDA were identified in the pilot; there were severe adverse events in a separate, subsequent campaign. Both MDA and IRS are acceptable and feasible interventions in Haiti. Although a significant impact of a single round of MDA/IRS on malaria transmission was not found using a standard pre- and post-intervention comparison, it is possible there was blunting of the peak transmission. Seasonal malaria transmission patterns, suboptimal IRS coverage, and low baseline parasitemia may have limited the effectiveness or the ability to measure effectiveness

Multiple sensors ensure guide strand selection in human RNAi pathways

Small RNAs guide RNA-induced silencing complexes (RISCs) to bind to cognate mRNA transcripts and trigger silencing of protein expression during RNA interference (RNAi) in eukaryotes. A fundamental aspect of this process is the asymmetric loading of one strand of a short interfering RNA (siRNA) or microRNA (miRNA) duplex onto RISCs for correct target recognition. Here, we use a reconstituted system to determine the extent to which the core components of the human RNAi machinery contribute to RNA guide strand selection. We show that Argonaute2 (Ago2), the endonuclease that binds directly to siRNAs and miRNAs within RISC, has intrinsic but substrate-dependent RNA strand selection capability. This activity can be enhanced substantially when Ago2 is in complex with the endonuclease Dicer and the double-stranded RNA-binding proteins (dsRBPs)-trans-activation response (TAR) RNA-binding protein (TRBP) or protein activator of PKR (PACT). The extent to which human Dicer/dsRBP complexes contribute to strand selection is dictated by specific duplex parameters such as thermodynamics, 5' nucleotide identity, and structure. Surprisingly, our results also suggest that strand selection for some miRNAs is enhanced by PACT-containing complexes but not by those containing TRBP. Furthermore, overall mRNA targeting by miRNAs is disfavored for complexes containing TRBP but not PACT. These findings demonstrate that multiple proteins collaborate to ensure optimal strand selection in humans and reveal the possibility of delineating RNAi pathways based on the presence of TRBP or PACT

siRNA Repositioning for Guide Strand Selection by Human Dicer Complexes

The human ribonuclease Dicer and its double-stranded RNA (dsRNA)-binding protein (dsRBP) partners TRBP and PACT play important roles in the biogenesis of regulatory RNAs. Following dicing, one dsRNA product strand is preferentially assembled into an RNA-induced silencing complex (RISC). The mechanism of strand selection in humans and the possible role of Dicer in this process remain unclear. Here we demonstrate that dsRNAs undergo significant repositioning within Dicer complexes following dicing. This repositioning enables directional binding of RNA duplexes, thereby biasing their orientation for guide strand selection according to the thermodynamic properties of the helix. Our findings indicate that Dicer is itself capable of sensing siRNA thermodynamic asymmetry regardless of the dsRBP to which it is bound. These results support a model in which Dicer employs two distinct RNA-binding sites-one for dsRNA processing and the other for sensing of siRNA thermodynamic asymmetry-during RISC loading in humans

Differential roles of human Dicer-binding proteins TRBP and PACT in small RNA processing.

During RNA interference and related gene regulatory pathways, the endonuclease Dicer cleaves precursor RNA molecules to produce microRNAs (miRNAs) and short interfering RNAs (siRNAs). Human cells encode a single Dicer enzyme that can associate with two different double-stranded RNA (dsRNA)-binding proteins, protein activator of PKR (PACT) and trans-activation response RNA-binding protein (TRBP). However, the functional redundancy or differentiation of PACT and TRBP in miRNA and siRNA biogenesis is not well understood. Using a reconstituted system, we show here that PACT and TRBP have distinct effects on Dicer-mediated dsRNA processing. In particular, we found that PACT in complex with Dicer inhibits the processing of pre-siRNA substrates when compared with Dicer and a Dicer-TRBP complex. In addition, PACT and TRBP show non-redundant effects on the production of different-sized miRNAs (isomiRs), which in turn alter target-binding specificities. Experiments using chimeric versions of PACT and TRBP suggest that the two N-terminal RNA-binding domains of each protein confer the observed differences in dsRNA substrate recognition and processing behavior of Dicer-dsRNA-binding protein complexes. These results support the conclusion that in humans, Dicer-associated dsRNA-binding proteins are important regulatory factors that contribute both substrate and cleavage specificity during miRNA and siRNA production

Dicer-TRBP complex formation ensures accurate mammalian microRNA biogenesis.

RNA-mediated gene silencing in human cells requires the accurate generation of ∼22 nt microRNAs (miRNAs) from double-stranded RNA substrates by the endonuclease Dicer. Although the phylogenetically conserved RNA-binding proteins TRBP and PACT are known to contribute to this process, their mode of Dicer binding and their genome-wide effects on miRNA processing have not been determined. We solved the crystal structure of the human Dicer-TRBP interface, revealing the structural basis of the interaction. Interface residues conserved between TRBP and PACT show that the proteins bind to Dicer in a similar manner and by mutual exclusion. Based on the structure, a catalytically active Dicer that cannot bind TRBP or PACT was designed and introduced into Dicer-deficient mammalian cells, revealing selective defects in guide strand selection. These results demonstrate the role of Dicer-associated RNA binding proteins in maintenance of gene silencing fidelity